As mobile devices have been increasingly developed, and the demand of such mobile devices has increased, the demand of secondary batteries has also sharply increased. Among them is a lithium secondary battery having high energy density and voltage and excellent preservation and service-life characteristics, which has been widely used as an energy source for various electronic products as well as the mobile devices.
On the other hand, various kinds of combustible materials are contained in the lithium secondary battery. As a result, the lithium secondary battery may be heated or explode due to the overcharge of the battery, the overcurrent in the battery, or other physical external impacts. That is, the safety of the lithium secondary battery is very low. Consequently, the lithium secondary battery includes a protection circuit module (PCM), which is connected to the battery cell for effectively controlling an abnormal state of the battery, such as the overcharge of the battery.
Generally, it is required for safety elements, including the PCM, to be maintained in electrical connection with electrode terminals of the battery cell and, at the same time, to be electrically isolated from other parts of the battery cell. Consequently, a plurality of insulative mounting members are required to construct such connection, which complicates the battery assembly process. Also, an adhesive is applied between the battery cell and the insulative mounting members such that the insulative mounting members are fixed to the battery cell by the adhesive. However, this coupling method reduces the strength of the battery. When physical impacts are applied to the battery cell, the reduction of the coupling strength induces the occurrence of a short circuit in the battery cell, with the result that the battery may catch fire and explode, and therefore, the safety of the battery is lowered.
For this reason, much research has been carried out to reduce the number of the insulative mounting members, which are coupled to the battery cell, and, at the same time, to improve the mechanical strength of the battery cell. For example, Korean Patent Application Publication No. 2002-077175 discloses a structure in which lock protrusions are formed at a battery case or a cover, which is mounted to the top of the battery case, and lock receiving parts are formed at the cover or the battery case, such that the cover is coupled to the battery case by the engagement between the lock protrusions and the corresponding lock receiving parts. Korean Patent Registration No. 0561298 discloses a structure in which concavo-convex parts are formed at the coupling interfaces between a bare cell and a battery component section located at the top of the bare cell such that the battery component section is coupled to the bare cell by the engagement between the concavo-convex parts of the bare cell and the corresponding concavo-convex parts of the battery component section. Also, Japanese Patent Application Publication No. 2006-140149 discloses a structure in which a protecting cover is coupled to a cell by the engagement between a conductive press member, mounted to the terminal part of the cell and a conductive insertion member, which is inserted into the conductive press member.
However, the above-described technologies have problems in that male and female type coupling members are additionally formed at the top of the bare cell and the bottom of the cell cover, and an additional insulation member is mounted between a protection circuit board, which is disposed between the bare cell and the cell cover, and the bare cell for accomplishing the electrical insulation between the protection circuit board and the bare cell.
In addition, Japanese Patent Application Publication No. 2006-04882 discloses a structure in which the bare cell is provided at opposite sides of the top thereof with coupling grooves, and the top cap is provided at the bottom thereof with coupling protrusions corresponding to the coupling grooves, such that the top cap is coupled to the bare cell by the forcible insertion of the coupling protrusion into the corresponding coupling grooves. Also, Korean Patent Application Publication No. 2006-32591 discloses a secondary battery constructed in a structure in which a top cover is mounted to a battery core, while a “structure supporting member” for supporting a protection circuit board is inserted into the top of the battery core, the battery core is provided at the top thereof with position holes, and the top cover is provided at the bottom thereof with position notches.
However, the above-described technologies have problems in that an additional member is inserted between the terminals of the battery cell and the protection circuit board for accomplishing the electrical insulation between the terminals of the battery cell and the protection circuit board, which complicates the assembly process. The problems will be described below in more detail.
Generally, a protection circuit module (PCM), including a protection circuit for controlling the overcharge, the overdischarge, and the overcurrent of the battery, is mounted to one side of a secondary battery where electrode terminals of the secondary battery are exposed to the outside. It is required for the PCM to be electrically connected to the both electrode terminals of the battery cell, and, at the same time, to be electrically insulated from the remaining parts of the battery cell such that the occurrence of a short circuit in the battery cell is prevented. Consequently, it is required for an insulative member to be inserted between the PCM board and the battery cell. In addition, it is required to provide an additional conductive member, such as a connection pin, for the electrical connection with the electrode terminals.
Also, in the technology for mounting the structure supporting member, for supporting the protection circuit board to the top of the battery core, the structure supporting member merely serves to guide the protection circuit board, such that the protection circuit board is mounted in position, and to support the protection circuit board. Furthermore, the protection circuit board is mounted to the bottom of the structure supporting member, with the result that the provision of an additional insulative member is still required.
The additional provision of the insulative/conductive members complicates the assembly process. Also, the additional disposition of a plurality of members between the battery cell and the top cap reduces the mechanical coupling strength.
Consequently, there is a high necessity for a technology that is capable of reducing the number of members mounted to the top of the battery cell to simplify the assembly process and securing stable coupling strength between the battery cell and the mounting members.